The location of user devices, and users of the user devices, is becoming part of many emerging products and services. From traditional applications (e.g., vehicle navigation) to augmented reality applications (e.g., location-based gaming and location-specific experiences) and precision advertising based on location, a location of a user device and a user of the user device is becoming as important as an identification of the user.
To date, user devices have relied on location solutions and technologies with widely varying degrees of accuracy. The most ubiquitous of these technologies is the Global Positioning System (GPS), or, with the addition of other international satellite constellations, is more generally known as the Global Navigation Satellite System (GNSS). A GPS signal in space will provide a worst case pseudo-range accuracy of 7.8 meters at a 95% confidence level, before any terrestrial biases, or errors, are introduced, such as ionospheric delay, tropospheric delay, receiver noise, receiver clock errors, and signal multipath. Multipath is an issue even for survey-grade receivers and antennas, but is much more so on low-end user devices, such as consumer smart phones which have linearly polarized antennas and not right hand circular polarized (RHCP) antennas which even the lowest end GPS receivers implement. As such, the accuracy of GPS-based location can vary significantly.
Many GPS receiver manufacturers have implemented techniques to mitigate the impact of these biases, or errors, on a resultant computed position. As such, many consumer-grade devices can achieve position accuracy of around three meters. Receivers which support reception of Satellite-Based Augmentation System (SBAS) signals can achieve accuracy better than three meters. In other cases, Local Area Augmentation Systems (LAAS), such as those used by airports, can further improve position accuracy. However, most consumer GPS devices in the market today, whether standalone GPS receivers or receivers integrated into consumer smart phones, do not support such correction services.
Most smart phones today support network-based positioning approaches which include determining position based on a cell tower to which a smart phone attaches, Third Generation Partnership Project (3GPP)-based location capabilities, such as timing advance and sounding reference signal, and cellular-received signal strength indicator. However, these approaches cannot provide accuracy below fifty meters at best and provide kilometer accuracy at worst.